1. Field of Invention
The present invention relates generally to microgrids for controlling small distributed energy resources (DERs). More specifically, the present invention relates to a self-managed microgrid with DC and AC inputs and outputs.
2. Description of Related Art
In general, microgrids are electric networks that are capable of deriving power from a number of sources including the conventional power grid, localized power generating capabilities and alternative power sources such as solar arrays and wind turbines. The microgrid can aggregate power from a number of sources, converting the different formats of power derived from multiple and diverse sources to common voltage and frequency formats that can be subsequently distributed to one or a number of loads. In addition, the microgrid can maintain the reliability of power to one or a number of loads in the face of changing power levels that are derived from the multiple and diverse sources. A microgrid can be coordinated to provide power from a variety of power sources and to provide power with greater reliability. For example, a microgrid can provide an alternate source of power to a site when there is an interruption in the power delivered by the conventional utility power grid. The power that the microgrid supplies to a site may be derived from a variety of sources including energy storage devices, alternative energy sources such wind or solar power, or from burning conventional fossil fuels. A description of prior art microgrid configurations is found in the whitepaper entitled “Characterization of Microgrids in the United States” prepared for Sandia National Laboratories by Resource Dynamics Corporation dated January 2005 and incorporated herein by reference in its entirety.
In general, there are prior patents and published patent applications directed to various aspects of microgrids. For example, U.S. Pat. No. 7,116,010 relates to the control of small distributed energy resources. U.S. Pat. No. 6,603,672 discloses a power converter system which allows various types of power formats to be derived from a variety of sources and converted in a predetermined manner to supplement power for a localized grid. U.S. Pat. No. 5,804,953 discloses a power converter for converting AC shore power for shipboard use, which converts a variety of shore voltages for shipboard use. U.S. Patent Application No. 2005/0105306 discloses a power converter that is adaptable for interfacing a variety of power sources with a three-phase AC power grid. U.S. Patent Application No. 2004/0124711 discloses a mobile power system housed in a standard freight container; the system distributes power in a plurality of configurations such as different voltage. U.S. Patent Application No. 2004/0061380 discloses a power management system for variable load applications. U.S. Patent Application No. 2002/0036430 discloses a local area grid for distributed power.
The disclosures in these prior patents and published patent applications is hereby incorporated herein by reference in their entirety. However, as described further below, none of these prior patents or published patent applications provides the solutions of the invention described and claimed in this application.